I've only seen one cabin crew with a tattoo...was on VirginBlue, but even his short sleeved shirt covered it up, until he reached up to close the overhead bin, and it peeked out. What was odd was the location...it was not on the outside of his bicep, but on the inside. I thought, "Marty, what possessed you to get a tattoo there??" It certainly didn't impact his ability to make a cabin announcement or sell drinks off of the trolley.
...but that's topic drift, sorry.
I know there is some sort of removal treatment out there, but it takes a few visits, and isn't cheap.